Component checking circuit for burner control apparatus



Jan. 9, 1951 J M MLSON 2,537,294

COMPONENT CHECKING CIRCUIT FOR BURNER CONTROL APPARATUS Filed Aug. 9, 1948 0 FLAME o DETECTOR o INVENTOR. JOHN M. WILSON & Mm

tion.

ar 9, i951 f1f COMPONENT CHECKING CIRCUIT FOR BURNER CONTROL APPARATUS John M. Wilson, Minneapolis, Minn., a ssignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware,

Application August a, 1948, Serial No. 413,254 f S'Claims. (cl; 158-28) The present invention relate to the control of a fuel burner. More particularly, the present invention-is concerned with a burner control which will maintain the burner inoperative in the event of flame failure or upon a false indication of flame: v In present day burner controls, it has been found desirable to provide safety devices which will render the controlled burner inoperative in the event that combustion fails to take place when the burner is started up or in the event that combustion fails after having been initiated.

I In addition to this, it has been found necessary to provide for rendering the burner inoperative' in the event that the device for indicating proper operation of the burner falsely indicates burner operation when there is no need for such opera-1 In my copending application for "Fuel Burner Safety Control System, Serial No. 731,998,

= flied March 3, 1947, I have disclosed an arrangement where a fuel burner is rendered inoperative in the event there is a flame failure or in the event that there is a false indication of flame by the flame detecting device. Ineither event, the burner control will maintain the burner inoperative until such time as the fault has been removed from the control. p

The present invention 'is concerned with a burner control of the type disclosed in my copending application. The present invention provides a burner control requiring a minimum of switch contacts for accomplishing the desired control functions and still maintains a high degree of safety. This is accomplished by provid-- ing a combustion or flame detector'which has overlapping in and out contacts for connecting lapping in and out contacts and which apparatus I is effective to: connect or disconnect a burner safety cutout device from a sourceof power whenever there is a condition of operation of the burner, or

the control, whichrequires such connection or disconnection.

, These and other obje' cts of the present invenv 7 tion will be understood upon a consideration of the following specification, claims and the single figure appended hereto.

The single flgure is a schematic illustration of the control.

Referring now to the single flgure, the numeral It represents a fuel burner which may be of any desired type and may be of the type havin an electric igniter for th fuel. For indicating-the need for operation ofthe fuel burner Ill, a thermostatic switching device ll may be provided which, when actuated, is efiective to cause the controls located within the housin I2 to energize the burner Ill. The burner ID will remain operative until such time as the thermostatic switching device N no longer indicates a need for operation of the burner.

The thermostatic switching device Il may be seen to consist of a bimetallic element l5 which 1 is effective upon temperature changes to move a the safety cutout device into and out of an energizing circuit in accordance with the presence or absence of a condition which might require rendering the burner inoperative.

It is therefore an object of the present invention to provide an improved burner control apparatus which requires a minimum of switch contacts and which is effective to maintain the burner inoperative in the event combustion fails or there is a false indication of flame.

Another object ofv the present invention is to provide an improved burner control which utilizes overlapping switch contacts to provide an apparatus having a minimum of switch contacts and which is effective to maintain the burner inoperative in the event of combustion failure or false indication of flame by the control apparatus.

Still anotherobject of the present invention is to provide an improved burner control apparatus which has a flame detection apparatus with o erswitch blade l6 into and out of engagement with an associated switch'contact IT.

The main controls of the present invention are 7 located in the housing l2. These controls in-- clude a source of power which is indicated by the numeral 2lland which may be an electric'transformer having a primary winding 2|, which may be connected to any suitable source of power, and a secondary winding 22 having a tap at 23. A main burner control relay for initiating operation of the burner is provided in a relay 24 and this relay consists of a relay winding 25 and switch blades 26 and 21 which are normal when deenergized so that blade 26 engages a contact 28 and blade 21 is out of engagement with a contact 29.

The numeral 30 represents a flame detector which may be of the type disclosed in my 00- I pending application Serial No. 465,476, filed November 13, 1942, for Control Device, now Patent No. 2,448,503, granted Aug. 31, 1948. Associated with this control device or flame detector is a photocell 3 l' which may be disposed in any desired manner to view the flame emitting from the,

burner l 0. The output relay for the flame detector 30 may be seen to consist of a relay winding 32 which is operative when energized to move a switch blade 33 from engagement with switch contact 34 into engagement with a switch contact 35. The switch contacts 34 and 35 are resiliently mounted contacts which are effective as overlapping contacts. These contacts cooperate with switch blade 33 so that when the switch blade is moved from the deenergized position, where it is contacting switch contact 34, through the intermediate position it will be engagin switch contact 34 as well as switch contact 35 so that there is always an electrical circuit completed through the switch blade 33 as it switches from the deenergized to the energized position or vice versa.

The numeral 40 indicates a safety cutout device for the'subject control apparatus and may be seen to consist'of a safety switch heater 4| which is effective, upon being energized for a predetermined length of time, to cause the bimetal 42 to be warped out from under the switch contacts 43 and 44 so that the same will separate and break an electrical circuit. For resetting the safety cutout device, a reset actuator 45 is provided. This actuator is so designed that depressing the actuator raises the contacts 43 and 44 from the return path of the bimetal 42 without allowing the contacts to close until the bimetal 42 is back in its normal position and the actuator is released. If the bimetal is not back in its original position it will be impossible for the switch contacts 43 and 44 to close.

Operation Considering the operation of the subject invention it will first be noted that the apparatus, as shown in the drawing, is in the deenergized position with the thermostatic device II not indicating a need for operation of the burner I and the burner control relay 24 and flame detection relay 30 both in the deenergized position. In the event that the space wherein is located the thermostatic device II should cool, the temperature of the bimetal l will decrease and cause the switch blade I6 to be moved into engagement with switch contact When this occurs an energizing circuit will be completed to the burner control relay 24 and this circuit may be traced from the upper terminal of the secondary winding 22 through conductor 50, switch contact l1, switch blade l6, bimetal I5, conductor 5|, relay winding 25, conductor 52, switch contacts 43 and 44, conductors 53 and 54, switch blade 33, switch contact 34, conductors 54 and 55, heater 4|, and conductor 55 back to the lower terminal of the secondary 22.

With this energizing circuit completed the relay' 24 will become energized and the switch blade 26 will move into engagement with its associated contact 29 to complete an energizing circuit to the burner ID. This energizing circuit may be traced from the input power line 58 through conductor 59, switch contact 29, switch blade 21, conductor 60, burner l0, and conductor 6| back to the other input power line 51. With this energizing circuit completed, the burner will be brought into operation and there should be a flame or combustion emitting from the burner In and, if so, this will be detected by the photocell 3| located in the output of the burner. When this flame is detected, the flame detection relay 30 will become energized and the relay winding 32 will move the switch blade 33 from engagement with switch contact 34 into engagement with switch contact 35. As mentioned above, this switching is accomplished without interruption of an electrical circuit through the switch blade 33 because of the fact that the contacts 34 and 35 are overlapping.

The need for this will beunderstood when it is noted that the energization of the flame detection relay connects the relay 24 ina relay maintaining circuit independent of the first traced circuit and independent of the safety cutout device 43. This relay maintaining circuit may be traced from the upper terminal of the secondary 22 through conductor 50, switch contact I1, switch blade I5, bimetal I5, conductor 5|, winding 25, conductor 52, switch contacts 43 and 44, conductors 53 and 54, switch blade 33, switch contact 35, and conductor 62 back to the tap 23 on the secondary 22. It will be noted that this last traced circuit does not include the safety cutout heater 4| for the circuit to this safety cutout heater was opened by the movement of the switch blade 33 from the switch contact 34.

The burner is now in the operating position with both the burner control relay 24 and the flame detection relay 30 energized. The burner will remain in the operating position until such time as the thermostatic device I I no longer indicates a need for operation of the burner I0. When the bimetal I5 of the thermostatic device I I has become heated sufllciently, the switch blade I6 will be moved from its engagement with switch contact I1 and the energizing circuit for the relay 24 will be opened. With the relay 24 deenergized,

the switch blade 21 will move out of engagement with switch contact 29 which in turn will cause the burner III to become deenergized. With burner I0 no longer operating there will be no flame detected by the photocell 3| and therefore the flame detection relay 30 will become deenergized and the switch blade 33 will move out of engagement with switch contact 35 and into engagement with switch contact 34 to put the control apparatus back in the condition it is shown upon the drawing. The apparatus is now in a condition for another operating cycle.

Operation upon flame failure Assume for the moment that the burner I0 and the control apparatus I2 were operating properly and are in the energized position with relay 24 energized and flame detection relay 30 energized. In the event there should now be a flame failure, the photocell 3| will no longer detect flame and the flame detection relay 30 will become deenergized. With relay 30 deenergized the switch blade 33 will move out of engagement with switch contact 35 and into engagement with switch contact 34. The movement of the switch blade 33 to this position will reconnect the safety cutout heater 4| into the energizing circuit of the relay 24 and this circuit ma be traced from the upper terminal of the secondary 22 through conductor 50, switch contact I1, switch blade I6, bimetal I5, conductor 5|, winding 25, conductor 52, switch contacts 43 and 44, conductors 53 and 54, switch blade 33, switch contacts 34, conductors 54 and 55, heater 4|, and conductor 55 back to the lower terminal of the secondary 22. In the event that combustion is not re-established in the burner III the continued energization of the safety cutout heater 4| will result in the warping of the bimetal 42 out from under the switch contacts 43 and 44. With said bimetal out from under the switch contacts 43 and 44 these contacts will separate and will open the energizing circuit for the relay 24 and the cutout heater 4|. With relay 24 deenergized the switch blade 21 will move out of engagement with switch contact 29 to open the energizing circuit for the burner Ill so that now both the control apparatus and the burner III will remain inoperative until such time as the reset actuator 45 is depressed to permit the closing of switch contacts 43 and 44. As mentioned above, these contacts cannot close until such time as the bimetal 42- has moved back to the normal position as it is shown upon the drawing.

Upon the closing of theswitch contacts 43 and 44, caused b the movement of the bimetal back to itsnormal position and; the subsequent depressingofthe, actuator, the energizing circuit to thefrelay 24 will again be completed. The apparatus' will then initiate operation of the burner and inthe event that the re-energization of the burner' does not establish combustion the safety cutout heater willagain warp the bimetal 42 from under the contacts 43 and 44 and the enbroken; r v

Obviously,'in the event that name is not established on the initial e'nergization of the relay 24 by the closing of the thermostatic device H, the safety'cutout heater 4| will be energized and will warp the bimetal in the manner mentioned above when flame was not established upon the 'de- 'ergizingfi circult for the relay 24.will: again be 1 pressing of the reset actuator 4i.

. Operation of false indication of fi'amd Assume-the apparatus has been operating properly withflboth the burner control relay 24 and' the flame detection relay .30 "energized and .now

'th6 thermostatic device indicates no further need foroperation of the; burner |0. '-This will' mean that the Switchblade i6 is moved out of engageand the Switchblade 21 moved out of engage-- mer t, withv contact 29 to cause deenergization of.

heater 4| and this circuit may be traced from v the tap 23-01 secondaryv 22 through conductor 62, switch contact 35, switch blade 33, conductors 54 and ,64,-switch blade 25, switch contact 28 conductors and-55, heater 4| and conductor the called for operation of the burner by the thermostatic device I I.

pointed out above. It will further be noted that a the control' apparatus employs only three switch contacts, independent of the burner control contacts, in accomplishing its shutdown upon flame failure and false indication of flame.

From the foregoin it will be seen that I have provided a burner control apparatus which requires a minimum of switch contacts while also providing an apparatus that will fail safe in the event of a flame failure or in the event there is a false indication of flame.

tion it will beobvious to those skilled in the art. that there are many ways in which the foregoing could be accomplished and therefore I intend to belimited solely by the scope of the appended claims.

I claim:

1. In a burner'control apparatus, a source of power. a safety switch device havin a pair of "switch contacts and a heater therefor which v I merit with switch contact, I]. It willfurther mean that the relay 24 will become deenergized heater is operative to cause opening of said safety switch contacts afteria predetermined length of time to render the control apparatus inoperative, a first relay which is operative when energized tocause en rgization of the burner, a second relay operated by means indicative of proper operation of the burner, said second relay havback .to the lower terminal of the secondary 22.- With this last traced circuit fcomp'leta the heater 4| will cause the binietalto vwarp toward the. right and. allow separation'l of the contacts 43 and {44 so that they willopen-circuit; As long as they areIopen-circuited it will-be. impossible to connect the burner control relay 24 in an energizing circuit and start operation of the burner.

It will further be noted that continued energization of the heater 4| will be had as long as e the switch blade 33 engagesswitch contacts and switch blade 26 engages contact 28 so that the subsequent depressin of the actuator or reset button will not result in the closing of the contacts 43 and 44 as the bimetal will be in the warped position and it will be impossible for'the contacts 43 and 44 to close upon the depressing and release of the actuator 45. This condition will exist until such time as the fault has been cleared from the flame detection relay 30' so that the switch blade33 moves intoengagement with switch contact, 34 to complete an energizing circuit for the burner control relay 24 upon the subsequent closing of the contacts 43 and 44 and ing a Switchblade and in and out overlapping contacts whereby said blade is always in engagement with one of said contacts, a first energizing circuit means for connecting said first relay to said power source adapted to be completed by 'means indicative of the need for operation of the burner, said circuit means including said safety switch heater and the out contact and switch blade of said second relay, second circuit means maintaining said first relay in an energizing circuit independentl of said safety switch heater upon proper operation of the burner, said second circuit means including said source of power and the in contact and switch blade of said second relay, and means including 'said first relay'when deenergized and the in contact and switch'blade of said second relay for connecting said safety switch heater in an energizing circuit when said second relay is falsely indicating proper operation of theburner.

2. In a burner control apparatus, a source of power; a safety switch device having a pair of switch contacts and a heater therefor which is operative to cause opening of said safety switch contacts upon continued energization for a predetermined length of time to effect deenergization of said control apparatus, a thermostatic switch adapted to be closed upon an indication for need of operation of the burner. a first "i lay having in and out switch contacts. saidlre lay adapted to cause energization of the jb Iner-"-" proper operation of the burner, a first electric switch contacts, the out switch contact of said While 1 have disclosed one particular embodiment of my inven-.

adapted to be completed without interruption off the energization of said relay, said second circuit including said thermostatic switch, the in contact of said overlapping contacts, and said source of power, and a third electric circuit adapted to be completed through said safety switch heater upon said first relay becoming deenergized and said second relay remaining in energized position, said third circuit including the in contact of said overlapping contacts, an out contact of said first relay and said source of power.

3; In combination in a burner control apparatus, a first relay for energizing the burner adapted to be energized by means indicative of the need for operation of the burner, a second relay which is rendered operative upon proper burner operation, means including contacts of said second relay for connecting said first relay in an energizin circuit and connecting said first relay in a maintaining circuit in uninterrupted sequence independently of any switch contacts of said first relay upon proper operation of the burner, a safety cutout device having an actuator and a pair of switch contacts with said actuator connected in said energizing circuit adapted when energized a predetermined length of time to efiect deenergization of said first relay by opening said pair of contacts, and means includin contacts of said first relay when deenergized and contacts of said second relay when in energized position for energizing said cutout device actuator continuously to prevent energization of said first relay.

4. In combination in a burner control apparatus, an electric transformer secondary winding having a tap thereon, a first relay for energizing the burner and adapted to be connected in an energizing circuit to the ends of said transformer winding by means indicative of the need for burner operation, a safety cutout device having an actuator and switch contacts in said last named energizing circuit and adapted to render inoperative said relay whensaid actuator has been energized a predetermined length of time, a second relay having overlapping in and out switch contacts, said second relay being energized upon proper operation of said burner, means connecting said out contact of said second relay in the energizing circuit of said first relay, means including the in contacts of said second relay for connecting in uninterrupted sequence said first relay in a maintaining circuit independently of any contacts of said first relay to said tap and discontinuing any circuit connection through said cutout device actuator, and means including contacts of said first relay when deenergized and the in contacts of said second relay for connecting said cutout device actuator in a circuit between said tap and an end of said transformer to render said apparatus inoperative when said second relay is falsely indicating proper operation of the burner.

5. In a burner control apparatus, a source of power, a first relay having an energizing circuit adapted when completed to cause energization 'of the burner, a safety cutout device having an actuator and switch contacts for rendering inoperative said e ectric means after said actuator has electric current passing therethrough for a predetermined length of time, a second relay rendered operative upon proper operation of the burner, said second relay comprising a switch blade and a pair of associated contacts which are overlapping as said switch blade is moved from the deenergized position to the energized position, means including said cutout device actuator and contacts and said second relay switch blade and deenergized position contact connected in the energizing circuit of said first relay, means adapted to complete the energizing circuit of said first relay to said source of power upon a need for burner operation, means including said second relay switch blade and energized position contact for connecting said first relay in a maintaining circuit independent of said outout device actuator and any switch contacts of said first relay to said source of power, and means including contacts of said first relay when in adeenergized position and said second relay switch blade and energized position contact for connecting said cutout device actuator in an energizing circuit to said source of power when said second relay is in operative position when there is no need for burner operation.

6. In a burner control apparatus, comprising in combination, a source of power, electrically energized first switch means for com leting an energizing circuit to the burner, electrically operated second switch means for indicating proper burner operation, said second switch means including switch contacts which are continuously in engagement when the means is moved from the energized to the deenergized position, a safety cutout device including switch contacts and a heater which when energized for a predetermined length of time will cause said switch contacts of said device to be operative to shut down said apparatus, means connecting said heater in a first energizing circuit to said source of power when it is desired to initiate burner operation, said means including only switch contacts of said second switch means and means for indicating a need for burner operation, means for maintaining said first switch means in an energizing circuit to said source independently of said heater, said last named means including said source of power and switch contacts of only said second switch means when in energized position, and means connecting said heater in a second energizing circuit only when said first switch means is in deenergized position and said second switch means is in energized position, said second energizing circuit being independent of said switch contacts of said cutout device so that said heater is continuously energized until said second switch means is in deenergized position.

7. In combination in a burner control apparatus, first switch means having an operator therefor for completing an energizing circuit to the burner and adapted to be energized by means indicative of the need for burner operation, second electrically operated switch means which are rendered operative upon proper burner operation, means including said second switch means for connecting the operator of said first switch means in an energizing circuit and connecting the operator of said first switch means in a maintaining circuit in uninterrupted sequence independently of any switch contacts of, said first switch means upon proper operation of the burner, a safety cutout device having an electrical actuator and switch contacts therefor in said energizing circuit adapted when energized a predetermined length of time to effect deenergization of the operator of said first switch means,

and means including contacts of said first switch means when said operator is deenergized and said second switch means when in energized position for rendering said cutout device actuator effective to prevent energization of said first switch means.

8. In a burner control apparatus, a source of power, a safety switch device having a pair of switch contacts and a heater therefore which is operative to cause opening of said safety switch contacts upon continued energization thereof for a predetermined length of time to efiect deenergization of said control apparatus, a control circuit adapted to be closed upon an indication ior need of operation of the burner, a first relay having in and out switch contacts, said relay adapted to cause energization of the burner upon becoming energized, a second relay having overlapping in and out switch contacts, said second relay normally being rendered operative upon proper operation of theburner, a first electric circuit for energizing said first relay, said circuit including said control circuit, said safety switch contacts, the out switch contacts of said overlapping switch contacts, said safety switch heater and said source of power, a second electric circuit for maintaining said first relay energized independently of said safety switch heater and adapted to be completed without interruption of the energization of said relay, said second circuit including said control circuit, the in contacts of said overlapping contacts and said source of power, and a third electric circuit adapted to be completed through said safety switch heater upon said first relay becoming deenergized and said second relay remaining in energized position, said third circuit including the in contact of said overlapping contacts, out contacts of said first relay, and said source of power.

JOHN M. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,102,618 Francis Dec. 21, 1927 2,254,984 Tate Sept. 2, 1941 

